1. Field of the Invention
The present invention relates to an electrically driven bicycle, and more particularly to an electrically driven bicycle which utilizes a driving power of a motor for assisting a human driving power or which utilizes the driving power of the motor as a main driving power for traveling. Especially, the present invention relates to an electrically driven bicycle in which the shape of a battery case and a configuration of a battery are improved so that a user can mount and dismount the bicycle smoothly and can travel in a safe state.
2. Description of the Related Art
In a conventional electrically driven bicycle of a certain type, a motor for driving wheels to assist a human driving power for traveling and a battery as a driving power source for the motor is mounted on the bicycle. As shown generally in FIG. 11, a main frame of the bicycle mainly includes a head pipe 104 on which a handlebar 105 is mounted, a standing pipe 102 on which a saddle 106 is mounted, and a main pipe (hidden by a battery case 110 in FIG. 11) bridging the head pipe 104 and the standing pipe 102, and the like. A structure is generally known in which the battery case 110 loaded with batteries is disposed on the main pipe, as shown in FIG. 11. The battery case 110 may be disposed in the front or in the rear of the standing pipe 102 instead of being disposed on the main pipe. In FIG. 11, the reference numeral 101 represents a driving section incorporating an electric motor, a speed reduction mechanism, a torque sensor, and the like; and the reference numeral 119 represents a frame cover that covers metal fittings provided in the main frame. The reference numeral 115 represents a cap for covering a charging connector. The cap 115 prevents intrusion of water and dust.
In the conventional electrically driven bicycle, the battery case is mounted over or under the main pipe, or in the front or in the rear of the standing pipe, as described above. Therefore, a structure is adopted in which a battery pack is prepared, for example, by making five rows each including four batteries connected in series, allowing all the batteries to be connected in series, and the battery pack is inserted into the battery case as it is. However, since each of the batteries has a diameter of about 33 mm, the height of the stacked batteries will be very high when the number of the stacked batteries is about three or more. Therefore, a problem arises such that there will be a large protuberance formed by the batteries over the main pipe or in front of the standing pipe, making it difficult to mount or dismount the bicycle.
Further, in the case where the batteries are to be disposed in the front or in the rear of the standing pipe, if the battery case is to be disposed on the chain case because of the existence of the chain case, the saddle must be mounted at a higher position, so that it will be very difficult for a less tall person to ride the bicycle because the feet cannot reach the ground so easily. On the other hand, in the case where the batteries are disposed in a space adjacent to the chain case, the bicycle is unbalanced, so that the user cannot ride the bicycle in a stable manner and, further, the batteries are not arranged in order, making the wiring complex and increasing the costs.
Moreover, if such a cap for covering the connector is provided, it may possibly be an obstacle in riding on the bicycle because the clothes or the feet of the user may be caught by the cap and, besides that, the appearance will be deteriorated, although the cap for covering the connector prevents intrusion of water and dust. Also, although the fixing member for fixing the battery to the main frame interlocks with a key, the fixing member can be actuated with the key even if the battery is not fixed to the main frame. Therefore, the user can allow the bicycle to run even if the battery is not firmly fixed to the main frame, so that the battery may possibly fall off while the bicycle is traveling.